Primavera otoño 2020 (Año LXIII Núms. 122-123)

horizontes@pucpr.edu Año LXIV Núm. 124-125 horizontes PRIMAVERA / OTOÑO 2021 PUCPR 80 During in vitro processes, tissue produced ethylene gas, leading to foliar abscission. Mahmoud et al. (2020) evaluated various silver ions - silver thiosulfate, silver nitrate, and silver nanoparticles - to inhibit ethylene production. They studied how the hardening agent of the culture medium and the tissue-culture vessel size affected gas exchange. One of the growth parameters that affected the most was the intensity of light. If the intensity was too high, it caused an increase in humidity and burned the tissue. Bowman and Albrecht (2021) investigated artificial light’s productivity on citrus crops in the nursery during winter. The controlled environment of the nursery protected against the weather to control vegetative growth. They installed light-emitting diodes and high-pressure sodium light structures to extend the luminous period to increase photosynthesis. They improved vegetative production and increased shoot proliferation. Temporary immersion A temporary immersion practice comprised flooding tissue with a liquid medium, leaving a time interval for the sample to be oxygenated. For lemon Citrus × latifolia , in vitro propagation protocols were optimized by employing a time interval. Bulbarela-Marini et al. (2019) experimented with a RITA™ liquid medium in 200 mL twin-flask bioreactors with five explant, five-minute immersion cycles for eight to twelve hours and obtaining up to six shoots per nodal segment. The in vitro container was accessible to cells and produced more sterile explants. Researchers used temporary immersion systems to recover biological compounds of commercial interest. Pramita et al. (2018) increased the concentration of compounds of interest from the medicinal plant Gynura procumbens . They temporarily immersed micro-propagated shoots into liquid medium bioreactors for twelve hours to increase their biomass and flavonoid compounds. The liquid medium providing the highest amount of biomass contained 2 mg / L of auxin, 4.6.8 mg / L of cytokinin, and 6 mg / L of kinetin with an immersion frequency of five minutes every three hours. The Murashige and Skoog medium supplemented with 2 mg / L of auxin, 8 mg / L of cytokinin produced the callus, resulting in the greatest flavonoid concentration from the bioreactor. Diagnosis test and treatment Knowing the phytopathogen attacking the crop was imperative to control any pest. Advances in molecular tests validated genetic identity and identified systemic diseases in citrus (Devi et al., 2021). One of the most lethal diseases in citrus crops was the Citrus tristeza virus, which had no chemical control. The virus could not invade the cellular tissue found at the apical tip. The apical tip could be grafted into a new parent plant to create a new plant with the same genetics but without the disease (Sing et al., 2018). Micrografting or shoot-tip grafting of the apical tip provided an effective physical treatment capable of generating new disease- free plants. The size of the apical tip was 0.3 mm to 0.5 mm, which was treated with 1.0 mg / L of kinetin to make the graft viable, and Murashige and Skoog medium with N6-benzylamine to promote the growth of the new plant. Micrografting was an efficient tissue purification technique proven. Conclusion In this review article, micropropagation of citrus cultivars suggested many difficulties. The growth promoters that showed the best results were of natural origin because these can function for more than one metabolic pathway in the cell. The basal medium with the best performance was Murashige and Skoog with vitamins from Gamborg B5, showing that plant